For a majority of the textures and some icon brushes that I've used, I've got them from the sites listed below:
Celestial Star, Aethereality, FEEL Designs, Fluffymonster, Colorfilter, Aun Exist Amor
For images, it ranges. Some I've gotten from all over, while others are ones that I've scanned/took screenshots of.
Code Geass Image Thread @ Animesuki.com forums
Random Curiousity (mainly for my Code Geass icon challenge, but that might get more pics from other series too, if I decide to make more icons from those series)
Crescendo - Though it IS my La Corda fansite and I wouldn't have to credit it, but I did take my screenshots from my site. :P
My-Neoromance (mainly for La Corda related pics, but might change in the future)
Official Japanese La Corda D'Oro 2 site
For icon text brushes, I've only recently downloaded a whole bunch as usually I just type in the text myself in Photoshop.
100x100 Brushes LJ Community - I would credit the individual people that made the brushes as well, but since I was kinda stupid enough to not pay attention to who actually made them as I was downloading them, I just decided to credit the community in general. I'll probably update this part in the future.
Below are the people that I got brushes and such for icons recently (so I've ACTUALLY kept track of it):
Last Updated: September 29, 2007
viciousgurl , wonderland__, ca_pris, starlit_designs, neke, amethystia, scarlite, jougen_no_tsuki, ghost_goodthing, viciousgurl, strawbrrygashs, papermache, artlessbakxsleepingswanx, shoegal_icons, dbzmerciter2005,chained_angel13, auctrix_icons, daisukicons, fragilecorpse, nv1978, paine_09, masquerade_arts, fearher, unwritten, yuna_ki, vampire_kiss, raynedanser, resunik, spikesbint,
If you see that I've used any of your brushes and such, but I haven't credited you, please let me know and I'll add your name to this list. ^^